Differential Equations in Abstract Cones

We extend the method of quasilinearization to differential equations in abstract normal cones. Under some assumptions, corresponding monotone iterations converge to the unique solution of our problem and this convergence is superlinear or semi–superlinear

SELF-SIMILARITY AND LAMPERTI CONVERGENCE FOR FAMILIES OF STOCHASTIC PROCESSES

We define a new type of self-similarity for one-parameter families of stochastic processes, which applies to certain important families of processes that are not self-similar in the conventional sense. This includes Hougaard Levy processes such as the Poisson processes, Brownian motions with drift and the inverse Gaussian processes, and some new fractional Hougaard motions defined as moving averages of Hougaard Levy process. Such families have many properties in common with ordinary self-similar processes, including the form of their covariance functions, and the fact that they appear as limits in a Lamperti-type limit theorem for families of stochastic processes.

Choices associated with automobiles for Men and Women: convergence or divergence?

The increase of the women purchase power has led some companies to adopt strategies of products differentiation as well as to produce specific products to the female public. The auto industry is not immune to this phenomenon, once the women represent, approximately half of the automobile sales in the country. Considering the consumption and the behavior differences between women and men, it has set the following question: are there differences between the choices associated to the automobile by men and the choices associated to the automobile by women? It has been presented to the participants items found in the people`s day-by-day, which are valorized by them, and the participants have been asked to choose and associate these items to the automobile. The results analysis revealed there are more similarities than differences between choices associated to the automobile by men ad choices associated to the automobile by women. The similarity between the choices suggests that the representations, the meanings and values assigned. to the car by men ana women are similar and thus the strategy of product differentiation does not apply to the automotive industry

Gerogescu-Roegen versus Solow/Stiglitz and the convergence to the Cobb-Douglas

The value of the elasticity of substitution of capital for resources is a crucial element in the debate over whether continual growth is possible. It is generally held that the elasticity has to be at least one to permit continual growth and that there is no way of estimating this outside the range of the data. This paper presents a model in which the elasticity is determined endogenously and may converge to one. It is concluded that the general opinion is wrong: that the possibility of continual growth does not depend on the exogenously given value of the elasticity and that the value of the elasticity outside the range of the data can be studied by econometric methods.

Evolutionary switch and genetic convergence on rbcL following the evolution of C4 photosynthesis.

Rubisco is responsible for the fixation of CO2 into organic compounds through photosynthesis and thus has a great agronomic importance. It is well established that this enzyme suffers from a slow catalysis, and its low specificity results into photorespiration, which is considered as an energy waste for the plant. However, natural variations exist, and some Rubisco lineages, such as in C4 plants, exhibit higher catalytic efficiencies coupled to lower specificities. These C4 kinetics could have evolved as an adaptation to the higher CO2 concentration present in C4 photosynthetic cells. In this study, using phylogenetic analyses on a large data set of C3 and C4 monocots, we showed that the rbcL gene, which encodes the large subunit of Rubisco, evolved under positive selection in independent C4 lineages. This confirms that selective pressures on Rubisco have been switched in C4 plants by the high CO2 environment prevailing in their photosynthetic cells. Eight rbcL codons evolving under positive selection in C4 clades were involved in parallel changes among the 23 independent monocot C4 lineages included in this study. These amino acids are potentially responsible for the C4 kinetics, and their identification opens new roads for human-directed Rubisco engineering. The introgression of C4-like high-efficiency Rubisco would strongly enhance C3 crop yields in the future CO2-enriched atmosphere.

Human capital spillovers, productivity and regional convergence in Spain

This paper analyses the differential impact of human capital, in terms of different levels of schooling, on regional productivity and convergence. The potential existence of geographical spillovers of human capital is also considered by applying spatial panel data techniques. The empirical analysis of Spanish provinces between 1980 and 2007 confirms the positive impact of human capital on regional productivity and convergence, but reveals no evidence of any positive geographical spillovers of human capital. In fact, in some specifications the spatial lag presented by tertiary studies has a negative effect on the variables under consideration.

Scale-dependent adaptive evolution and morphological convergence to climatic niche in Californian eriogonoids (Polygonaceae)

Aim Macroevolutionary patterns and processes change substantially depending on levels of taxonomic and ecological organization, and the resolution of environmental and spatial variability. In comparative methods, the resolution of environmental and spatial variability often defines the number of selective regimes used to test whether phenotypic characteristics are adaptively correlated with the environment. Here, we examine how investigator choice of the number of selective regimes, determined by varying the resolution of among-species variability in the species climatic niche (hereafter called ecological scale'), influences trait morphological diversification among Eriogonoideae species. We assess whether adaptive or neutral processes drive the evolution of several morphological traits in these species. Location South-western North America. Methods We applied a phylogenetic framework of three evolutionary models to four morphological traits and the climatic niches of Eriogonoideae (in the buckwheat family, Polygonaceae). We tested whether morphological traits evolve in relation to climate by adaptive or neutral process, and whether the resulting patterns of morphological variability are conserved or convergent across the clade. We inspected adaptive models of evolution under different levels of resolution of among-species variability of the climatic niche. Results We show that morphological traits and climate niches of Eriogonoideae species are not phylogenetically conserved. Further, adaptive evolution of phenotypic traits is specific to climatic niche occupancy across this clade. Finally, the likely evolutionary process and the level of detectable niche conservatism change depending on the resolution of environmental variability of the climatic niche. Main conclusions Our study demonstrates the need to consider both the resolution of environmental variability and alternative evolutionary models to understand the morphological diversification that accompanies divergent adaptive evolution of lineages to climatic conditions.

Phylogenomics of C(4) photosynthesis in sedges (Cyperaceae): multiple appearances and genetic convergence.

C(4) photosynthesis is an adaptive trait conferring an advantage in warm and open habitats. It originated multiple times and is currently reported in 18 plant families. It has been recently shown that phosphoenolpyruvate carboxylase (PEPC), a key enzyme of the C(4) pathway, evolved through numerous independent but convergent genetic changes in grasses (Poaceae). To compare the genetics of multiple C(4) origins on a broader scale, we reconstructed the evolutionary history of the C(4) pathway in sedges (Cyperaceae), the second most species-rich C(4) family. A sedge phylogeny based on two plastome genes (rbcL and ndhF) has previously identified six fully C(4) clades. Here, a relaxed molecular clock was used to calibrate this tree and showed that the first C(4) acquisition occurred in this family between 19.6 and 10.1 Ma. According to analyses of PEPC-encoding genes (ppc), at least five distinct C(4) origins are present in sedges. Two C(4) Eleocharis species, which were unrelated in the plastid phylogeny, acquired their C(4)-specific PEPC genes from a single source, probably through reticulate evolution or a horizontal transfer event. Acquisitions of C(4) PEPC in sedges have been driven by positive selection on at least 16 codons (3.5% of the studied gene segment). These sites underwent parallel genetic changes across the five sedge C(4) origins. Five of these sites underwent identical changes also in grass and eudicot C(4) lineages, indicating that genetic convergence is most important within families but that identical genetic changes occurred even among distantly related taxa. These lines of evidence give new insights into the constraints that govern molecular evolution.

Human capital spillovers, productivity and regional convergence in Spain

This paper analyses the differential impact of human capital, in terms of different levels of schooling, on regional productivity and convergence. The potential existence of geographical spillovers of human capital is also considered by applying spatial panel data techniques. The empirical analysis of Spanish provinces between 1980 and 2007 confirms the positive impact of human capital on regional productivity and convergence, but reveals no evidence of any positive geographical spillovers of human capital. In fact, in some specifications the spatial lag presented by tertiary studies has a negative effect on the variables under consideration.

Economic and social convergence in Colombia

GDP has usually been used as a proxy for human well-being. Nevertheless, other social aspects should also be considered, such as life expectancy, infant mortality, educational enrolment and crime issues. With this paper we investigate not only economic convergence but also social convergence between regions in a developing country, Colombia, in the period 1975-2005. We consider several techniques in our analysis: sigma convergence, stochastic kernel estimations, and also several empirical models to find out the beta convergence parameter (cross section and panel estimates, with and without spatial dependence). The main results confirm that we can talk about convergence in Colombia in key social variables, although not in the classic economic variable, GDP per capita. We have also found that spatial autocorrelation reinforces convergence processes through deepening market and social factors, while isolation condemns regions to nonconvergence.

Human Capital Spillovers Productivity and Regional Convergence in Spain

This paper analyses the differential impact of human capital, in terms of different levels of schooling, on regional productivity and convergence. The potential existence of geographical spillovers of human capital is also considered by applying spatial panel data techniques. The empirical analysis of Spanish provinces between 1980 and 2007 confirms the positive impact of human capital on regional productivity and convergence, but reveals no evidence of any positive geographical spillovers of human capital. In fact, in some specifications the spatial lag presented by tertiary studies has a negative effect on the variables under consideration.

Climate Change and Transregional Convergence: Carbon Markets in North Amer ica

National policies in North America have not been drafted properly to address the problem of climate change, following the impasse of international negotiations. Facing this scenario, new alternatives emerge with the leadership and participation of new actors. Local governments in North America, especially of British Columbia, Ontario and Quebec, have been developing strategies to face climate change and emissions reduction in parallel to the national efforts and the global governance strategies. These local governments have developed a transregional approach that has resulted in the creation of regional institutions such as the Western Climate Initiative, the Regional Greenhouse GasInitiative and the Midwestern GreenhouseGas Reduction Accord.Their main goal is to establish regional carbon markets to mitigate and adapt to climate change impacts in a cost-effective way. In spite of these efforts, these initiatives have faced the overlapping problem among them and with national and globalstrategies. The goal of this research is to explore how these carbon markets have developed convergence policies. Convergence among these markets is expressed in their offset system and in secondary markets.

Species divergence and trait convergence in experimental plant community assembly

Despite decades of research, it remains controversial whether ecological communities converge towards a common structure determined by environmental conditions irrespective of assembly history. Here, we show experimentally that the answer depends on the level of community organization considered. In a 9-year grassland experiment, we manipulated initial plant composition on abandoned arable land and subsequently allowed natural colonization. Initial compositional variation caused plant communities to remain divergent in species identities, even though these same communities converged strongly in species traits. This contrast between species divergence and trait convergence could not be explained by dispersal limitation or community neutrality alone. Our results show that the simultaneous operation of trait-based assembly rules and species-level priority effects drives community assembly, making it both deterministic and historically contingent, but at different levels of community organization.